Lightning arrester



Juy 28, will c. im. STRQUF LIGHTNNG ARRESTER Filed June 20, 1941 2SheeLS-Sheel" 2 Patented `uly 28, 1942 UNITED STATES PATENT OFFICELIGHTNING ARRESTER Charles L. Stroup, Oak Park, Ill.

Application June 20, 1941, Serial No. 398,880

4 Claims.

My invention relates, generally, to circuit interrupting devices and ithas particular relation to lightning arresters. The present inventionconstitutes an improvement over the lightning arrester constructiondisclosed in my copending application, Serial No. 321,868, led March 2,1940, and represents the commercial embodiment of the construction thereshown.

An object of my invention is to prevent bursting of the insulatinghousing forming a part of the lightning arrester as a result of pressuregenerated therein on the formation of an arc.

Another object of my invention is to provide for venting the gasexpansion spaces within the insulating housing radially inwardly.

Another object of my invention is to provide for Venting the housing ofthe lightning arrester downwardly at its ends.

Still another object of my invention is to provide for clamping thevarious parts within the tubular insulating housing in predeterminedrelation thereto in such manner as to resist displacement resulting frompressure generated in the arrester on formation of an arc therein and tofacilitate manufacture of the arrester.

Other objects of my invention will, in part, be obvious and in partappear hereinafter.

For a more complete understanding of the nature and scope of myinvention, reference can be had to the following detailed descriptiontaken in connection with the accompanying drawings in which:

Figure 1 is a View in side elevation, certain parts being broken away toshow the interior details of construction, of a preferred embodiment ofmy invention;

Figure 2 is a viewin side elevation of the arrester unit that isinserted in the outer waterproof insulating housing of the lightningarrester shown in Figure 1;

Figure 3 is a view, in end elevation, of the unit shown in Figure 2;

Figure 4 is a longitudinal sectional View of the unit shown in Figure 2,certain portions being shown in elevation;

Figure 5 is a detail sectional view taken along the line 5-5 of Figure4;

Figure 6 is a view, in end elevation, of one of the end caps employedfor closing the ends of the lightning arrester and Venting the samedownwardly; and

Figure '7 is a detail sectional View taken along the line 'I 'I ofFigure 6.

Referring now particularly to Figure 1 of the Cil drawings, it will beobserved that the reference 55 character I0 designates, generally, alightning arrester construction which is intended for use ondistribution circuits ranging upwardly in voltage from 2,300 volts. Theconstruction includes a metallic bracket formed by two cooperating partsII and I 2. The lower part I2 of the bracket is arranged to be mountedon a cross-arm or the like so that the lightning arrester constructionI0 is mounted in a substantially horizontal position as shown.

The upper part of the bracket I I carries a pin type insulator I3 fromwhich a terminal I4 projects upwardly for connection to the line orconductor to which the lightning arrester construction I0 is to beconnected. A nut I5 threaded on terminal I4 serves to hold a clampmember I6' against a conductor disposed thereunder and on top of ametallic washer I'I. A gap I8 is provided between the metallic washer IIand an arcing horn I9 so as to prevent the application of line voltageto the arc extinguishing parts of the lightning arrester construction I0which will be described hereinafter.

A lightning arrester assembly, indicated generally at 22, is providedWithin a weather-proof housing 23, of frangible insulating material suchas glass or porcelain, for extinguishing arcs that may occur onoperation of the lightning arrester construction I0. The lightningarrester assembly 22 is 0f unitary construction and can be assembled assuch for insertion in the housing 23.

In Figures 2, 3, 4, and 5 of the drawings, the details of constructionof the lightning arrester assembly 22 are shown. As there illustrated,particularly in Figure 4, the assembly comprises a tubular housing 24 ofinsulating material such as ber and it has intermediate its ends animperforate plug 25 of insulating material such as liber. The housing 24and plug 25 are formed of iiber or other similar material so as to becapable of evolving an arc extinguishing medium, such as Water vapor,when subjected to the heat of an arc for assisting in extinguishing thesame. The plug 25 has a Contact t with the inner surface of theinsulating housing 24 so that the juxtaposed surfaces as indicated at 20are close together. It is along these surfaces that an arc is formed onoperation of the device. Because of the extremely limited space for thearc, relatively great pressures are generated which, together with thearc extinguishing medium evolved from the juxtaposed surfaces of thehousing 24 and plug 25, serve to quickly extinguish the arc. Usually thearc is extinguished within one-half cycle or less of the alternatingcurrent, such as a (iO-cycle current, with which distribution systemsare usually energized.

At the ends of the imperforate plug 25 are electrodes 21 and 28 which,as shown, are substantially less in diameter than the diameter of theplug 25. The arc is formed between the electrodes 21 and 28 and isrequired to make two changes in direction in order to follow the pathprovided over the juxtaposed surfaces of the housing 24 and plug 25. Asdescribed in my copending application, referred to hereinbefore, thisfacilitates the extinction of the arc. Conductor rods 29 and 39 extendaxially outwardly from the electrodes 21 and 28. As shown, they may beformed integrally with the electrodes 21 and 28 or they may be formedseparately and threaded into the electrodes 21 and 28 as desired. Itwill he observed that the arcing horn I9 is secured to the conductor rod29 by means of a nut 3| and a lock washer 32y as shown in Figure 1 ofthe drawings.

The electrodes 21 and 28 are provided with shoulder portions 33 and 34facing outwardly against which the inner ends of sleeves 35 and 36 ofinsulating material abut. The sleeves 35 and 35 are preferably of fiber.They are spaced from the adjacent inner surfaces of the insulatinghousing 24 so as to form gas expansion spaces 31 and 38 into which gasesevolved during arc extinction can expand. The outer ends of the gasexpansion spaces 31 and 38 are closed by threaded metallic sleeves 39and 40 which react against washers 4I and 42 that abut the outer ends ofthe sleeves 35 and 36. The metallic sleeves 39 and 48 cooperate withinternal threads at the ends of the insulating housing 24 and areprovided with recesses 43 and 44 for receiving a suitable spannerwrench.

When the threaded metallic sleeves 39 and 40 are located as illustrated,they serve to hold the parts inside of the insulating housing 24securely in place in proper spaced relationship. When properlytightened, they place the insulating housing 24 somewhat in tension andthe plug 25y electrodes 21 and 28, and sleeves 35 and 36 somewhat incompression.

The gas expansion spaces 31 and 38 are vented by apertures 45 and 46which open radially inwardly from the gas expansion spaces 31 and 38into the interior of the sleeves 35 and 36, The interior of the sleeves35 and 36 is vented to the atmosphere as will be presently apparent.

As indicated hereinbefore, relatively high pressures are generated alongthe juxtaposed surfaces of the housing 24 and plug 25 when an arc isformed between the electrodes 21 and 28. With a view to preventing theinsulating housing 24 from bursting, due to these pressures, a sleeve 49of insulating material, such as ber, is provided around both the housing24 and plug 25 underneath a reenforcing ring or sleeve 50 of steel. Thereenforcing ring or sleeve I] fits closely over the sloev 49 which inturn fits closely over the housing 24 so that bursting of the housing 24in this region is effectively prevented. Since the insulating plug 25 isrelatively short as compared to the length of the housing 24, thereenforcing .ring or sleeve 5I! is correspondingly short, being longenough as shown to extend somewhat bevond the ends of the plug 25, andtherefore it does not substantially reduce the external dielectricproperties of the housing 24.

As shown in Figure 1 of the drawings, the insulating housing 24 is ofthe same length as the water-proof housing 23. It is held therein bysuitable metallic end caps 53, the details of construction of which areshown in Figures 1, 6, and '1 of the drawings. Each of the end caps 53is provided with a shoulder portion 54 which abuts the outer end of theinsulating housing 24 and a forwardly extending flange portion 55 whichsurrounds the adjacent end of the insulating housing 24. The radiallyprojecting shoulder 56 abuts a ring of suitable packing 51 whichinterflts with a suitable recess in the adjacent end of the water-proofhousing 23. Each of the end caps 53 provides a space 58 whichcommunicates through the threaded metallic sleeves 39 and 4I), Figure 4,into the interior of the sleeves 35 and 36 which communicates with thegas expansion spaces 31 and 38 through the radial apertures 45 and 46,as previously described. The space 58 in each of the end caps 53 isvented downwardly through a plurality of apertures 59 in the form ofmilled slots in its undersurface. The slots 59 are preferably relativelynarrow so as to prevent the entrance of insects and so forth into theinterior of the lightning arrester construction I0.

The end cap 53 of the lefthand end of the water-proof housing 23 is heldin place by the nut 3| and lock washer 32 which also holds the arcinghorn I9 in position as previously described. The end cap 53 at therighthand end is held in place by a nut 60 and a lock washer 6I.

The conductor rod 30 at the righthand end of the water-proof housing 23is arranged to be connected to ground. For this purpose a conductor issecured to the conductor rod 30 by means of a nut 62 which serves tofasten a clamp member 63 securely against a conductor placed underneathit against a washer 64.

In operation, on the occurrence of an over- .voltage such as is causedby a lightning or switching surge, the gap I8 breaks down and an arc isformed between the electrodes 21 and 28 along the juxtaposed surfaces ofthe housing 24 and plug 25. Because of the confined space in which thearc is formed due to the contact t between the housing 24 and plug 25and further because of the arc extinguishing medium evolved from them,the arc is quickly extinguished and the gases incident thereto expand inthe spaces 31 and 38 provided therefor and are expelled through theapertures 45 and 46 to the atmosphere through the vents 59 in the endcaps 53.

As soon as the arc between the electrodes 21 and 28 is extinguished, thearc at the gap I8 is also extinguished.

Since certain changes can be made in the foregoing construction anddifferent embodiments of the invention can be made without departingfrom the spirit and scope thereof, it is intended that all matterdescribed herein and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a lightning arrester, in combination, a tubular housing, a plugWithin said tubular housing spaced a substantial distance from at leastone end thereof, said housing and plug being formed of insulatingmaterial capable of evolving an arc extinguishing medium due to the heatof an arc, electrodes at the ends of said plug between which an arc maybe formed along the juxtaposed surfaces of said housing and plug,conductor means extending out of said one end of said housing from theadjacent electrode therein, and a sleeve of insulating materialextending outwardly from said adjacent electrode :and spaced from theinner surface of said housing to provide therebetween a gas expansionspace the outer end of which is closed, there being one or moreapertures in said sleeve adjacent its outer end opening radiallyinwardly for venting said space.

2. In a lightning arrester, in combination, a relatively long tubularhousing, a relatively short plug within said housing intermediate itsends, said housing and plug being formed of insulating material capableof evolving an arc extinguishing medium due to the heat of an arc,electrodes at the ends of said plug between which an arc may be formedalong the juxtaposed surfaces of said housing Iand plug, conductor meansextending from each electrode out of its end of said housing, and asleeve of insulating material extending outwardly from each electrodeand spaced from the inner surface of said housing to providetherebetween gas expansion spaces the outer ends of which are closed,there being one or more apertures in each sleeve 'adjacent its outer endopening radially inwardly for venting said spaces.

3. In a lightning arrester, in combination, a tubular housing, a plugwithin said tubular housing spaced a substantial distance from at leastone end thereof, said housing and plug being formed `of insulatingmaterial capable of evolving an arc extinguishing medium due to the heato-f an arc, electrodes at the ends of said plug between which an arc maybe formed Yalong the juxtaposed surfaces of said housing and plug,conductor means extending out of said one end of said housing from theadjacent electrode therein, a sleeve of insulating material extendingoutwardly from said adjacent electrode and spaced from the inner surfaceof said housing to provide therebetween a gas expansion space,

the outer end of said sleeve being spaced from said one end of saidhousing and there being one or more apertures in said sleeve adjacentits outer end opening radially inwardly for venting said space, andclamp means disposed interiorly of said housing at said one end thereofincluding means reacting against the adjacent end of said sleeve forholding the same in a predetermined position in said housing and closingthe outer end of said gas expansion space.

4. In a lightning arrester, in combination, a relatively long tubularhousing, a relatively short plug within said housing intermediate itsends, said housing and plug being formed of insulating material capableof evolving an arc extinguishing medium due to the heat of an arc,electrodes at the ends of said plug between which an arc may be formedalong the juxtaposed surfaces of said housing and plug, a conductor rodextending axially out of each end of said housing from the adjacentelectrode therein, a sleeve of insulating material extending outwardlyfrom abutting relation with each electrode and spaced from the innersurface of said housing to provide therebetween a gas expansion space,the outer end of each sleeve being spaced from the adjacent end of saidhousing and there being one or more apertures in each sleeve adjacentits outer end opening radially inwardly for venting each space, andclamp means disposed interiorly of said housing at each end and adaptedto react against the adjacent end of the sleeve thereat for holding thesame in predetermined position in said housing and closing the outer endof each expansion space.

CHARLES L. STROUP.

